You should know better than to think that translating like this:
Japanese -> English -> Japanese
would give identical results all of the time.
Taito means Far East, as in the Orient.
Tengai Makyou (天外魔境) roughly translates to "Evil boundary outside the heavens", so they obviously chose (rather loosely) an English phrase that had a nice ring to it.
In case you folks weren't familiar, "East of Eden" is a famous novel by John Steinbeck, so I'm pretty sure the makers of Tengai Makyou combined the phrases "far east" and "East of Eden" into a single pun.